Ruler and tracer for arcs of circles



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B.,B.NOYBS. RULBR AND TRACER FOR ARCS 0F CIRCLES. No. 593,236.

Patented Nov. 9, 1897.

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ELLISBRA DFORD NOYES, OF PORTSMOUTH, VIRGINIA.

RULER AND TRACER FOR ARCS OF CIRCLES.

SPECIFICATION forming part of Letters Patent No. 593,236, dated November 9, 1897.

Application filed February 15, 1896- Serial No. 579,349. (No model.)

To all whom it may concern:

Beit known that LELLIsBRnDroRD NoYEs, a citizen of the United States, and a resident of Portsmouth, in the county of Norfolk and State of Virginia, have invented certain new and useful Improvements in Tracers and Rulers, of which the following is a specification, reference being had to the accompanying drawings, forming apart thereof, in which similar letters of reference indicate corresponding parts. i

This invention relates to curve tracers and rulers; and the object thereof is to provide an improved device of this class which is simple in construction and operation and by means of which any desired arc of a circle may be found.

The invention is fully disclosed in the following specification, of which the accompanying drawings form a part, in which Figure 1 is a plan view of my improved curve ruler or tracer, showing also the method of the operation thereof, the position of the parts for drawing a given are of a circle being shown in dotted lines. Fig. 2 is a front edge view of the device; Fig. 3, a plan view of my improved curve ruler 0r tracer, showing the parts thereof in their normal position; Fig. 4, a side View of one of the weights employed in connection therewith; Fig. 5, a plan view of the upper end of said weight, and Fig. 6 a diagrammatic view designed to illustrate the principle of the construction and operation of my improved ruler.

My improvement is based upon the principle that the external angle D G C, Fig. 6, formed at the intersection of two chords of an arc of a circle, is one-half the external angle A B 0, formed by two tangents drawn from the extreme points F and O of the same are of a circle, and the further principle that any two chords drawn from the points F and C to any point of the are between them subtend equal angles.

My improved instrument or curve-tracer is composed of two separate rules H and K, Fig. 1, which may be provided with any desired scale or scales on their outer edges and have bearing swivehwheels attached to their outer end for the purpose of holding them clear of the surface on which the curve is to be drawn, and these rulers are held by frames h and It,

provided with shoulders or projections h and 10', respectively, between which the rulers are secured by means of set-screws L.

Pivotally connected with the outer shoulder or projection in of the frame 76 is a segmental arm M, and pivotally connected with the outer shoulder or projection h of the frame It is a similar segmental arm 0. The segmental arm 0 is provided with a scale de signed to represent ten degrees for each five degrees of actual arc, and the segmental arm M is provided with a zero-mark or Vernier, as shown at m. The frames by which the rules H and K are supported or retained in position are pivotally connected at P by a joint constructed with a hole through its center, and said joint may be raised above the frames which hold the rules by curved arms P rigidly attached to the frames, the object of this being to provide for the insertion of a pin, pointer, pen, or pencil P by which the curve may be traced while keeping the rules near the surface on which the tracing is performed. I also provide an ordinary clamp and tangent R, to which a small carrier may be added, if desired, by which the position of the segmental arms M and O is regulated, this device being of well-known construction and requiring no further description.

The pin or pointer P may be replaced by a pen or pencil, and the instrument is so made that when set at zero, as shown'in Fig. 3, the rules H and K form a straight line and the inner ends thereof point to the center of the circle of which the adjacent parts of the arms M and 0 form half the circumference.

I also employ the usual lead weights S, as shown in Figs. 4 and 5, comprising a body portion having projecting heads composed of jaws S between which is mounted a wheel 8 and one or both of said jaws being provided with a pointer S The operation will be readily understood from the foregoing description when taken in connection with the accompanying drawings.

In order to trace any required are of a circle, set the angle of the arm provided with the scale which represents ten degrees for each five degrees of actual arc to the external tangent angle A B G. Then set the pointers on the lead weights, two of which are employed, at tangent points F O, and pressing the rules lightly against the wheels on the lead weights draw the are required.

In the arrangement of the parts shown in Fig. 1 in dotted lines the curve-ruler is set to connect two tangents of five inches each, which intersect at an angle of forty-eight degrees, and, as will be understood, the five inches may represent different distances, according to the scale adopted. that different angles and distances may be used, according to the given requirements of the case in hand- In order to describe an arc of a circle through three given points, the lead weights should be set at the outside points and the pen 01' pencil P at the center approximately at right angles to the tangent,

with the pointer at the beginning of the curve, one at each end, and it will thus be seen that I accomplish the object of my inventionby means of a device which is simple in construction and operation and Well adapted-to accomplish the result for which it is intended.

It is evident that many changes in and modii fications of the construction herein shown 5 and described may be made without-departj ing from the spiritof my inventionor'sacrt;

ficing its advantages.

Having fully described my invention, 1 claim and desire to secure by Letters Patcut- 1. The herein-described curve tracer orruler comprising two straight rulers which; are adjustably supported in frames which are I pivotally connected'at their inner ends, said frames being each provided at its outer end witha curved or segmental arm, one of which is provided with a scale, andthearrangement Q of said parts being such that when the rulers I are held in astraight line the segmental arms form the half of a circle, to the center of which the inner ends of the rulers point, said seg-; mental arms being connected by means'of a; clamp and tangent, and the inner ends of the frames which support said rulers being con-i nectedbyineans of a circular hinge through It will be seen which is formed a hole for the introduction of a tracing-pencil, substantially as shown and described.

2. The herein-described curve tracer or ruler, comprising two straight rulers which are adj ustably supported in frames which are pivotally connected at their inner ends, said frames being each provided at its outer end with a curved or segmental arm, one of which is provided with a scale, and the arrangement of said parts being such that when the rulers are held in a straight line the segmental arms form the half of a circle, to the center of which the inner ends of the rulers point, said segmental arms being connected by means of a clamp and tangent, and the inner ends of the frames which support said rulers being connected by means of a circular hinge through which is formed'a hole for the introduction or a tracing-pencil, and means to compel the tracing-point thereof to trace a predetermined are, substantially as shown and described.

3. The herein-described curve tracer or ruler, comprising two straight rulers which are adj ustably supported in frames which are pivotally connected at their inner ends, said frames being each provided at its outer end with a curved or segmental arm, one of which is provided with a scale, and the arrangement of said .parts being such that when the rulers are held in a straight line the segmental arms form the half of a circle, to the center of which the inner ends of the rulers point, said segmental arms being connected by means of a clamp and tangent, and the inner ends of the frames which support said rulers being connected by meansof a circular hinge through which is formed a hole for theintroductionot' a tracing-pencil, and means to compel the a wheel, said jaws being also provided with a pointer, substantiallyasand for the purpose set forth.

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